---
cve: "CVE-2026-86205"
severity: "MEDIUM"
cvss: 5.4
epss: "4.6%"
vendor: "Generic Security"
kev: false
exploited: false
published: "2026-09-06 12:17:15"
tags: [cve, security, medium]
source: tsecurity.de CVE-Dossier
exported: "2026-09-06T19:21:39+02:00"
---

# CVE-2026-86205

> 5.4 MEDIUM

## Beschreibung

h3 versions before 2.0.1-rc.18 contain an open redirect vulnerability in the redirectBack() utility that fails to sanitize protocol-relative paths in the Referer header pathname. Attackers can craft a same-origin URL with a double-slash path segment that passes origin validation but produces a Location header interpreted by browsers as a protocol-relative redirect to an external domain.

## CVSS-Vektor

```
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Erforderlich | good |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Gering | warn |
| I Integrität | Gering | warn |
| A Verfügbarkeit | Keine | good |

## Referenzen

- <https://github.com/h3js/h3/security/advisories/GHSA-fp4x-ggrf-wmc6>
- <https://www.vulncheck.com/advisories/h3-before-2.0.1-rc.18-open-redirect-via-redirectback>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-86205) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_